Electrochemical recovery of silver from waste aqueous Ag(I)/Ag(II) redox mediator solution used in mediated electro oxidation process

The paper presents a process for the electrochemical recovery of silver(Ag) by electro deposition on the electrode surface from the waste solutions of Ag(I)/Ag(II) redox system in nitric acid medium used for the mediated electrochemical process. Electrochemical recovery was carried out in an undivided cell with DSA-O₂ electrodes at room temperature condition. At an optimized current density of 12 A/dm², 99% of Ag recovery efficiency was achieved with high yield and low energy consumption. Experimental runs were made in order to observe the performance of the Ag recovery process. The operating conditions like current density, temperature and Ag(I) concentration of the electrolyte, the acid concentrations, agitation rate and inter-electrode distance were optimized.     

Ultrasonic spray deposition for production of organic solar cells

Recent improvements of organic photovoltaic power conversion efficiencies have motivated development of scalable processing techniques. We compare chlorobenzene and p-xylene, as solvents with similar bulk properties, in a case study of ultrasonic spray depositions of bulk heterojunction layers in photovoltaic devices. Structure and morphology of spray-deposited films are investigated via small-angle X-ray diffraction and optical microscopy. Unique phases are observed in bulk heterostructure films sprayed from p-xylene. Films sprayed from chlorobenzene resulted in higher device efficiencies than p-xylene due to large differences in film morphologies. Carrier loss mechanisms are also investigated. Post-production annealing increases power conversion efficiency to 3.2% when chlorobenzene is used.     

Nitrogen dry deposition to Lake Superior and Lake Michigan

Nitrate (NO₃^?) levels in Lake Superior have increased from historic levels of about 5?μM to its current concentration of about 25?μM. The atmosphere makes a substantial contribution to the nitrogen budgets for Lake Superior and Lake Michigan. This study provides a more well-defined estimate of nitrogen dry deposition rates derived from the measurement of over-water concentrations, and in situ meteorological measurements, which were input into the Resistance Model. We obtained a nitrogen dry deposition rate of [(3.41?±?2.26)?×?10⁷?kg?N/yr; (5.90?±?3.91)?kg?N/ha/yr] over Lake Michigan, and [(1.54?±?1.06)?×?10⁷?kg?N/yr; (1.87?±?1.27)?kg?N/ha/yr] over Lake Superior. Nitric acid (HNO₃), which originates from the combustion of fossil fuels, contributes 84% of the total nitrogen dry deposition to Lake Michigan; and 66% to Lake Superior. Ammonia (NH₃), which originates from agricultural activities and gasoline combustion, is the second highest contributor of nitrogen dry deposition to both lakes: contributing 13% to Lake Michigan and 32% to Lake Superior. The nitrogen dry deposition is approximately 68% of the nitrogen wet deposition over Lake Superior, and approximately 80% of wet deposition over Lake Michigan. The over-water dry deposition velocity of HNO₃ and NH₃ were also evaluated. We obtained morning deposition velocities of 0.099?cm/s for NH₃ and 0.095?cm/s for HNO₃; and afternoon values of 0.137?cm/s for NH₃ and 0.132?cm/s for HNO₃. Another key finding is that the atmospheric concentrations of nitrogen compounds near Lake Michigan and Lake Superior have decreased since 2003.     

Thermodynamic and experimental study of chemical bath deposition of Zn(S,O,OH) buffer layers in basic aqueous ammonia solutions. Cell results with electrodeposited CuIn(S,Se)2 absorbers

This paper presents a thermodynamic study of Chemical Bath Deposition (CBD) of zinc sulphide based films in aqueous ammonia solutions. The aim is a better understanding of ammonia and temperature effects on the deposition conditions and films composition. The formation of solid phases has been predicted by means of the precipitation conditions of ZnO, Zn(OH)₂ and ZnS as a function of temperature between 298 and 333 K. Films have been deposited according to calculated diagrams and preliminary results on solar cells based on electrodeposited CuIn(S,Se)₂ layers have been demonstrated. Composition and thickness of the films have been extracted to link the theoretical study with experiments.     

Theoretical studies of preparation of core-shell nanoparticles by electrochemical metal deposition

In the present work we discuss the statistical mechanical framework for predicting the decoration of metallic nanoparticles using electrochemical methods, in thermodynamic equilibrium. It is found that depending on the interactions between the two metals, controlled decoration may be achieved for core-shell nanoparticles in undersaturation and oversaturation conditions. The concept of underpotential deposition is discussed for the case of nanoparticles, with the finding that this phenomenon may be size dependent.     

ION REDISTRIBUTION NEAR THE POLAR GROUPS IN THE LANGMUIR WETTING PROCESS

The theoretical analysis of electrostatic interactions and ion redistribution in the close vicinity of the three-phase contact line shows their important role in the Langmuir wetting process. To provide a sufficient rate for the ion transfer, which is intended to neutralize the interfacial charge, the concentration and potential distributions deviate from the equilibrium. As a consequence, during the deposition process the adhesion work, and hence the contact angle, are defined by the local ionic concentrations near the three-phase contact line. The concentration profiles and the electro-diffusion ion fluxes induced during the Langmuir wetting process are strongly dependent on the subphase composition and on the monolayer properties. The results of the analysis are in a good agreement with the experiments.     

Sparse nanowire arrays for facile transport measurements

Nanowires can be electrodeposited into partially etched porous alumina templates such that only a very small number of nanowires reach the top surface of the template. This allows transport measurements of small clusters or single nanowires in their alumina matrix by connecting leads to the hemispherical domes marking the protrusion of nanowires on the surface. Copper, nickel, and silver nanowires have been synthesized in this manner, and a more general synthesis method is proposed.     

Comparison of the Electrical Characteristics of PZT and SBT Thin Films

The electrical properties of lead zirconate titanate (PZT) and strontium bismuth tantalate (SBT) thin films are compared for nonvolatile random access memory applications. PZT thin films have high switchable polarization with poor fatigue resistance and higher leakage current densities as compared to SBT thin films deposited on platinized silicon substrates. Characterization of these films in terms of their domain dynamics under application of sub-switchable and switchable electric fields give valuable insight about the observed differences in the electrical behavior. In the present work the dielectric behaviors of SBT and PZT thin films at sub-switchable electric field were analyzed in terms of Rayleigh law. The reversible and irreversible polarization component of switchable polarization was separated by the measurement of capacitance-voltage (C-V) and polarization hysteresis loops. The conduction mechanisms in these films were evaluated by measuring field dependence of leakage current densities at various temperatures. The observed differences in electrical properties are explained in terms of the intrinsic defects and defect-domain interaction of these two materials.     

Crystallization of Zirconium-Rich PLZT Thin Films Below 500°C

The general problem of processing zirconium-rich lead-lanthanum-zirconate-titanate (PLZT) thin films at the commonly used temperatures between 600 and 650 C is lead-oxide loss, leading to the formation of a non-ferroelectric, surface pyrochlore-type phase. To avoid lead-oxide losses due to sublimation and/or the interaction of the film with the substrate, it is desirable that the annealing temperatures are as low as possible. Our goal was to study and prepare perovskite PLZT 9.5/65/35 (Pb 0.858 La 0.095 Zr 0.65 Ti 0.35 O 3 ) thin films below 500 C. At 400 C the growth of the perovskite phase follows the parabolic law typical of diffusion controlled processes. During prolonged annealing growth continues until the limiting stoichiometry of the perovskite phase with regard to the PbO is reached. We conclude that, even at this low temperature the amount of PbO in the film is the critical factor in the crystallization of the perovskite phase.     

沥青质沉积机理研究综述

沥青质沉积机理及其如何防治已成为石化行业急需解决的问题,但国内外研究学者对沥青质沉积机理并未形成统一的认识。对沥青质相关研究进行调研整理,首先对沥青质的定义与结构进行阐述,之后对沥青质沉淀、聚集作用、沉积过程模型及各种影响因素对沥青质沉积的影响进行综述,为日后学者研究沥青质沉积机理提供理论指导。